Erythromycin A and common derivatives are widely used and exhibit desirable activity against a number of gram-positive pathogens. Since some pathogens are less susceptible than others to these drugs, high doses of these antibiotics are occasionally necessary in the treatment of serious or widespread infections. In other isntances, combinations of these drugs with other antimicrobials must be employed. As a result, there is a continuing search for antibiotics which are more potent against certain organisms than those currently used. Desirably, such drugs will have an improved therapeutic ratio, which is the ratio of the effective therapeutic or prophylactic dose to the toxic dose, usually expressed in terms of the ED.sub.50 /LD.sub.50 ratio.
It is an object of this invention to provide novel compounds which are derivatives of erythromycin, and which have greater in vitro and in vivo potency against certain organisms, such as Hemophilus influenzae, than erythromycin A, and preferably greater than the more toxic derivatives of erythromycin A.
This and other objects of this invention will be more fully understood by reference to the following disclosure.